Structural changes by drawing of Bombyx mori silk fibroin were investigated by means of X-ray diffraction, differential scanning calorimetry, and thermomechanical analysis (TMA). At the early stage of the drawing, the degree of orientation of silk fibroin molecules increased with increasing draw ratio and the content of the randomly coiled region decreased. This orientation may be attributed to the formation of hydrogen bonds between the C=O and N-H groups of adjacent molecules. Further drawing accelerated the formation of the β-sheet structure. When the draw ratio increased more than 6 times, the degree of orientation of silk fibroin molecules increased up to the value comparable to those of the silk fibroin fiber in which a β-pleated-sheet structure with anti-parallel chains was formed. The rate of the thermal contraction of the specimen observed on the TMA curves decreased with increasing draw ratio in the temperature range of 230-260°C and the length of the specimen remained constant due to the high thermal resistance associated with the intersheet and interchain hydrogen bonds, when the pleated sheet structure was formed. At this stage, the specimen exhibited the endothermic shoulder peak at about 310°C and an additional major endothermic peak at 282°C.

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The effect of copper on the crystal form of silk fibroin crystals (Fcp) treated in the cupriethylenediamine solution (Cu-EDA-1) was studied. The Fcp was obtained by precipitation from the aqueous fibroin solution with chymotrypsin. Another precipitate (Fcplc) was obtained when the Fcp was dissolved in cupri-ethylenediamine solution (Cu-EDA-2) and then dialyzed.
The copper content in the Fcp was confirmed to be very low by atomic absorption analysis (below 0.03mgCu/g fibroin). The X-ray diffraction pattern of the Fcp showed that the Fcp was the β-crystalline form. In the case of Fcplc, the higher pH in the Cu-EDA-2, the more copper was adsorbed in the fibroin. While the amount of copper adsorbed in Fcplc was seriously affected by the copper concentration of the Cu-EDA-2. Fcplc including a large amount of copper (1.5-4.5mgCu/g fibroin) showed the α-crystalline form, while that containing a small amount of copper (below 0.05mgCu/g fibroin) was the, β-one. The results of X-ray diffraction and differential thermal analysis showed that the Fcplc including a large amount of copper has the same structure as the -type fibroin of silk grand

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Biodegradation behaviors of poly (L-glutamic acid) fibers were performed in vitro and in vivo, including biodegradation and mechanical properties to simulate in vivo fiber degradation, as well as biocompatibility behavior.
Unoriented and oriented poly (L-glutamic acid) (PLGA) fibers were spun from concentrated aqueous poly(L-sodium glutamate) solution. The conformational characterization was performed by wide-angle X-ray diffraction measurement. Copoly (L-glutamic acid/γ-methyl-L-glutamate) fibers were also prepared by saponification reaction of the side chains of poly(γ-methyl-L-glutamate) by sodium hydroxide in EtOH-water mixture. PLGA fibers were found to be extensively degraded by pepsin in a buffer solution at pH=1.6 and 37.0°C. It was pointed out that the unoriented PLGA fiber (α and β) digested faster than the oriented PLGA fiber (β), and that the rate of degradation of copolymer fibers by pronase E (pH=7.4) was extensively depressed by the γ-methyl-L-glutamate side chain.
Next, the enzymatic degradation of these fibers was processed on the surface of the fibers, and the rate of degradation of this case was analyzed by the first order reaction rate concerning the effective surface area of the fiber. This fact was also demonstrated from the direct observation by scanning electron microscopy. The behavior of the decrease in tensile strength as a function of the decrease in fiber weight was different from that of the non-enzymatic degradable fibers such as polyglycolic acid.
The tissue reactions were observed to be extremely slight, and these fiber samples have been replaced by the connective tissue safely during the absorption process.

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Two component random copolypeptide (PHEG-co-PMLG) fibers consisting of N-hydroxyethyl-L-glutamine and γ-methyl-L-glutamate with different copolymer composition were prepared by a partial aminolysis reaction of poly (γ-methyl-L-glutamate) fibers with 2-amino-1-ethanol, followed by crosslinking reaction with 1, 8-octamethylenediamine. The tensile properties of these hydrophilic fibers were highly dependent on the degree of swelling Q_w in PBS solution (pH=7.4), and showed a typical elastomeric behavior in wet-state. Biodegradation behaviors of PHEG-co-PMLG fibers were performed in vitro, including enzymatic degradation and mechanical properties to simulate in vivo fiber degradation. The rate of degradation of these hydrophilic fibers in vitro by pronase E was also highly dependent on Q_w of fibers. It was pointed out that the enzymatic degradation of these fibers was processed on the surface area of the fibers, and that the rate of degradation of these fibers was analyzed by the first order reaction rate concerning the effective surface area of the fiber. This fact was also demonstrated from the direct observation by scanning electron microscopy. The behavior of the decrease in the tensile strength as a function of the decrease in the fiber weight was characteristic for the enzymatic degradable fibers and quite different from that for the non-enzymatic degradable fibers such as polyglycolic acid fiber. The tissue reaction was observed to be extremely slight for these hydrophilic fibers, which have been replaced by the connective tissue quite safely during the absorption process.

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The polymerization of ethylenimine (EI) by means of vapor phase reaction onto woody fibers (Asplund defibrated pulp, and bleached kraft pulp) previously treated in a corona discharge was studied. The following results were obtained: 1). EI was remarkably polymerized onto the fibers by corona treated in air, but slightly polymerized for the untreated fibers. 2). Asplund defibrated pulp (A. P.) which contained lignin was more readily activated by the corona pretreatment than bleached kraft pulp (K. P.) of hard wood, and the amount of the polymerized ethylenimine of the former was reached to about twice that of the latter. 3). The lower moisture content of the sample during the polymerization of EI was advantageous, and in these conditions the PEI of about 90% of total polymerized EI was fixed on the fibers. So, the composites were obtained in dry state. 4). The polymerization was not accelerated by the corona pretreatment in nitrogen. 5). By the corona treatment in air the substrate was oxidized, and low molecular oxidation products which were easily eluted with water were formed. The amount of the oxidized groups, especially carboxyl groups, increased with an increase in the time of treatment and the PEI content of the resulting woody fiber-PEI composites was proportional to the amount of carboxyl groups produced. These indicated that the polymerization of EI onto woody fibers occurred effectively by the corona pretreatment in air, and by a mechanism of ring-opening addition polymerization of EI catalyzed by the carboxyl groups produced.

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When a pulp, especially chemical pulp, is repeatedly disintegrated in water, dewatered and dried for several times, the mechanical properties of handsheets are considerably deteriorated. This paper mainly deals with changes in the micro-structure of fibre cell wall by recycling. Changes in recycled fibres were determined by the solute exclusion and the mercury intrusion methods as well as the electron microscopy. Moreover, loading of titanium dioxide in lumina of recycled fibres was investigated. Following results were obtained.
(1) Tensile strength of handsheets from recycled fibres could be partly restored by beating.
(2) By beating the recycled pulp, the pore volume in cell wall of the pulp fibres could be partly recovered. The mercury penetration volume into the handsheet increased with recycling and decreased by additional beating.
(3) It was observed that morphological changes such as delamination and crack formation in cell wall of the recycled fibre were enhanced by additional beating.
(4) The amount of TiO₂ loaded in pulp fibres increased with recycling upto 3rd time and decreased after 5th time. The amount of TiO₂ retained in handsheets seemed to be dependent on bulkness, flexibility and rigidity of fibres.

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As noble solid supports for enzyme immobilization, partly glycolated chitosans were prepared from chitosan. α-Amylase was immobilized on a glycolchitosan with the aid of cross-linking agent glutaraldehyde. The maximum activity yield of enzyme immobilized on glycolchitosan with a degree of substitution of glycol groups of 0.78 was 28%, compared with that on chitosan of 20%.
The optimum pH for the conversion of starch to reducing sugars by the immobilized enzyme on glycolchitosan was approximately 6. This was lower than that for the conversion with free enzyme. The optimum temperature for the conversion using immobilized enzyme was 60°C, similar to that for the conversion with free enzyme. Immobilized α-amylase on glycolchitosan retained about 80% of the maximum enzyme activity after repeated use of 6 times.

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The weak base type anion exchange adsorbent was prepared by introducing the amino group to the cotton yarn. The adsorbent was for the water recycle model system in order to remove reactive dyes in the rinsing water. The chemical treatments were carried out in aqueous solutions for introducing the ion exchange group into the inside of the fiber matrix. Cotton yarns were graft-copolymerized with 5% acrylamide using cerium salt as an initiator at 50°C. The maximum grafting ratio was 23.3%. The grafted amide group was transformed into the amino group through Hofmann-degradation using sodium-hypochloride. The nitrogen content of the sample was 1.5%. The breaking strength of the ion exchangeable cotton yarn decreased to 75% of the original cotton yarn through the above chemical treatments. The colour removal from rinsing waste water used in the model system was examined with the treated yarn. It was found that the capacity of this yarn for adsorbing hydrolyzed reactive dyes increased in acidic solution and at a high temperature. The colour removal of this yarn was the same as that of activated carbon powder according to the results of the batch method. In contrast, the colour removal with this yarn was ten times higher than that with activated carbon granules in the column method.

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